Free to use, no sign-up, works on any phone.
It is a 20-lesson tutor rather than a test: there is no timer, no WPM figure and no score at the end. The focus is correct finger placement, so the page gives you a pair of animated hands and a virtual keyboard instead of speed statistics.
The finger that should press the next character lifts up and glows orange, and the matching key on the on-screen keyboard is outlined at the same moment. The left hand is tinted blue and the right hand green, a finger turns red and drops while you hold that key, and the home row keys A S D F J K L and semicolon carry a marker so you can find the resting position.
They run from the home row (F J, D K, S L, A and semicolon, then a review) to the top row, the bottom row, a full-sentence drill, capitals with Shift, the numbers 1 to 5 and 6 to 0, and finally symbols. Any lesson can be opened directly from the row of buttons at the top, and finishing one loads the next automatically after about two seconds, with the last lesson looping back to the first.
The character turns red and the cursor stays where it is, so you cannot move on until you press the correct key. Letters are matched without regard to case, so in the capitals lesson you should hold Shift yourself even though a lowercase letter is accepted, while the symbols lesson does require the real Shift combination.